Inductance coil



Feb. 10, 1931. J. J. JAKosKY 1,792,375

INDUCTANCE COIL Original Filed Dec'. 20. 1925 ATTRNEYS.

Patented Feb. 10, 19,31

UNITED STATES PATENT OFFICE TOEN if.- JAKO'SKY, .OF LOS ANGELES, CALIFORNIA, ASSIGNOR T0 INTERNATIONAL PRE- CIIITATION COMPANY, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF CALI-I FORNIA INDUCTANCE COIL Original application led December 20, 1925, Serial No. 78,472. Divided and thisA application filed April 26, 1927. Serial No. 186,636.

This invention relates to inductance or reactance coils for connection 1n electrical c1rcu1ts, and particularly to co1ls for use 1n the prevention or elimination of high 'fre-- quency oscillations in such circuits, for the purpose of eliminating radio interference or the operating circuits of electrical precip1 itators as described in my above mentioned application, itis of advantage to produce absorption rather than reflection of the high frequency currents. That is to say, it is desirable to absorb the energy of the high frequency oscillation within the coil, rather than to cause such energy to be reflected. back into 'the circuit. The use of ordinary choke coils often causes high voltages to build up ahead yof the choke due to reiiection phenomena and to the high reactance of the cholre. Such high potentials, if superimposed on the low frequency voltage of an electrical precipitator circuit may cause disruptive peelr voltages and thus impair the operation of the precipitator. A

It is therefore yadvantageous in such cases to employ a coil having an iron core, as such iron core not only increases the effective resistance due to hysteresis losses but` also de creases the inductance due to the iron core acting to a certain extent as a short circuited secondary winding for the choke coil. This latter effect may be enhanced by providing an external rather than internal iron core. By this means therefore the absorption of energy due to the eiective resistance of the choke may readily be increased to the desired ext-ent' without introducing an excessive `coil, which may be termed an. absorber coil,

which has a maximum energy absorbing effect by virtue of the provision of an iron core therein, and which at 'the same time presents. a minimum tendency to conduct high frequency current because of the coilto-core capacity. This object is accomplished by the use of an external iron core composed ,of a plurality of short sections, each insulated from one another, and each forming a complete short circuited secondary. ln a coil of this type the high frequency currents passing by capacity from the coil to any section of the core are substantially prevented from. passing along thecore due to the interposition of the insulating layers which present highl resistance and low capacity.

.ln circuits, such as electrical precipitator circuits, it is often desirable toconnect inductance coils directly in a transmission line, and a further object of this invention is to provide an inductance coil which is adapted for connection in this manner and is of sufficient mechanical strength to support and transmit the strain or stress existing in such a line due to the weight thereof between supports. A coil of this construction may be.

termed a strain type in ductance coil. When connected in a conducting linefor between two conducting members, it forms mechanically an integral part of the line but interposes an electrical inductance of the de Fig. 4c is a transverse section on line 4--4 in Fig. 3.

The coil shown in Figs. 1 and 2 consists essentially of a central supporting tube 1 of bakelite or other insulating material around which are wound a suihcient number of turns of wire to form the coil itself, indicated at 2. The winding may be made to have any desired value of inductance. In one case, l have used for example a 25,/8 inch bakelite tube with a 3000 michrohenry winding consisting of No. 26 D. C. C. wire. The winding is preferably of the single layer type, instead of multi-layer, as it has been found that multi-layer coils have much higher inter-coil capacity than do single' layer coils. A plurality of external iron rings 3 are laced around the winding 2 and are spacedp therefrom as by means of strips 4 of bakelite or other insulating material. Rings S-may be spaced apart in any suitable manner, for example by means of insulating material such as cord 5 wound around between such rings. The entire coil, after construction, should be dipped in varnish and baked. i c

The absorber may be considered electrically as comprising a 3000 michrohenry primary winding, around which are placed a pluralit of one-turn short circuited secondary coi s, constituted by the iron rings 3 extending completely around the coil. The external rings, being made of iron, act also to decrease the reluctance ofthe external part of the magnetic circuit, and hence increase the magnetic flux, and the sectional construction of this external core acts to 'reduce the passage of. high frequency currents due to internal capacity to the minimum value consistent with fairly close cou ling.

The effective resistance of t .e absorber coil varies approximatel with the square of the fre uency. The higlier transients therefore su er much greater attenuation than the low frequency ulsating rectified current such as used in e ectrical precipitator operation. As a result, the losses for the rectified current are reduced to a minimum, while the losses for the undesirable high frequency vtransients are great. It can be shown that the high frequency resistance of the absorber coil may be many 'thousandsof ohms, while the low frequency resistance for the rectified pulsating currentvis only a fraction of an 'ohm In any coupled circuit the ap arent re- 4actance of the Primary is always c anged by the'l resence. o the secondary, and it may-'be furt er shown that the effective inductance ofthe primary -is decreased bythe urrent flowing in the secondarycircuit. Considerfective resistance and inductance in coupled circuits of this type, it is seen that the -eect of the currentv owing in the secondary is to increase the resistance of the primary circuit, and to decrease its self induction.

It may also be shown. that these effects vary directly with the square of the frequency. The low frequencies suffer only slightly from-the small change in effective resistance, whileffor lthe higher frequencies the eective resistance is greatly increased andthe self-iductance is greatly decreased. This increase 1n resistanceand decrease 1n inductance tend to prevent oscillations and to already been shown.

'absorb or dissipate the energy thereoffas has As shown in Figs. 3 and 4 the absorber j coil may also be constructed with end connectingmembers for connection at an intermediate point in a conducting line or between two conducting members so as to support and transmit the stress or strain between such conducting members. rEhe coil may in this case comprise as before a central supporting tube 1 of bakelite or other insulating material, an inductance coil 2 wound upon said tube, longitudinal spacing strips 4, iron rings 3 and suitable spacing means 5 such as bakelite rings between said ironrings. An end connecting member 1() isgfurther provided at each end of the coil, each of such connecting members having `a hollow cylindrical portion 11 fitting over the end of the balrelite tube and also comprising a projection or lug 12 provided with suitable means Asize and number to support the weightlof the conducting line. The centralsupporting member l1 must also be of suiiicient strength to sulpport and transmit the stress due tothe The electrical connection between winding 2 and end members 10 weig t of the line.

tube by means of metallic t ma be providedby carrying each'end of sai winding, as indicated at 17,. out through groove 18 in the bakelite tube and through hole 19 in end member 10, and solderingor otherwise securing' the end, of wire 17 to the Iend member as at 20. It will be seen that when a coil of this type is connectedl between two portions of a conducting line it forms mechanically an integral part of the line but interposes a hi h frequency impedance ofthe desired value tilierein.' c c I claim: 4 yL V1. .An absorber coil comprising a wire lfiliduction coil, a plurality of iron rings extending completely around said coil and insulated therefrom, said iron rings being spaced from each other, whereby each of said vrings forms a short circuited single turn secondary Winding for said induction coil, and all of said iron rings together serving to constitute an external core of low magnetic reluctance for said coil.

2. An absorber coil comprising a Wire induction coil, an iron core surrounding said coil and insulated therefrom, said ironcore being divided longitudinally into a plurality of sections spaced apart from one another, a

, supporting member of insulating material 'extending throughout the length of. the coil, and connecting members secured mechanically to the ends of said supporting member and connected electrically to the ends of said induction coil.

In testimony ,whereof I have hereunto subscribed my name this 18th day of April, 1927.

JOHN J. J AKOSKY. 

